Deep Freeze

Good communication and collaboration between Preservation and other library units is key to being able to do our work effectively. The Stacks Department headed off a major disaster by discovering a minor one in the days before Parks Library shut down for the winter break (December 24-January 4). The sprinkler system in the stacks sprung a leak at a seam in the overhead pipes, drenching one shelving unit holding about 100 books. Stacks discovered the problem on a Monday morning walk-through, and immediately called Preservation.

Several of the wettest books, at the center of the shelving unit, were already exhibiting serious mold growth. The leak had probably occurred over the weekend or at the end of the previous week, since mold growth can start at around 48 hours of extreme moisture.

The Conservation staff sprang into action, wrapping items loosely in waxed paper before packing them into crates for transport to the Library Storage Building, where our grocery case style “holding freezer” is located. The books were stored in the holding freezer over the break.

After break, the books were moved into the Wei T’o Freeze Dryer. The extreme cold kills the mold spores, but also reduces the warping that moisture can cause in books. The books are frozen solid and then dried through sublimation as the temperature inside the freeze-dryer is elevated slowly, in cycles, over the course of a few months. The books are just about dry and ready to come out of the freezer now. They’ll be individually assessed to determine whether they should be saved and treated or discarded.

We expect to discard about a half a dozen of the moldiest books. The remainder will be brushed and vacuumed with a HEPA filter under the fume hood. Where possible, stains will be reduced with vinyl eraser crumbs. Each book will then be labeled on the inside cover to warn future users that it has been treated for mold.

The first day of spring may be only three weeks away, but Iowa is still in a deep freeze, as you can see in this picture our Conservation Technician, Mindy, shared of her home.

The accumulated snowfall raises concerns about potential water and mold problems in basements and other low-lying storage areas during the spring thaw (see our Spring 2010 Thaw Tips page). Iowa temperatures have been nearly as low as those inside the Wei T’o freezer this winter — if only we could sublimate all this snow and freeze-dry roads and sidewalks as easily as we do our collection materials.